JPH05129200A - Manufacture of semiconductor film - Google Patents

Abstract

PURPOSE:To form a single crystal semiconductor film on an insulated substrate with no restriction in the material of the insulated substrate CONSTITUTION:Seeds based on the projection 4a of a single crystal Si wafer 4 having equal crystal axes are supplied from the surface side of an amorphous Si thin film 3' so as to perform solid phase growth from these seeds. Thereby, a single crystal Si thin film 3 having a fixed orientation to be decided by the single crystal Si wafer 4 is formed. Later, two sheets of wafers 1, 4 are oxidized while being stuck together and forming an oxide film 5 in the contact part followed by being dipped into an HF water solution so as to remove the oxide film 5 by etching. Thereby, the wafer 1, in which a single crystal Si thin film 3 is formed, and the single crystal Si wafer 4 for the seed are separated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to SOI (Silicon On I)
The present invention relates to a method for manufacturing a semiconductor thin film in an nsulator structure, particularly a single crystal semiconductor thin film.

[0002]

2. Description of the Related Art Conventionally, various methods for realizing an SOI structure have been proposed. As a typical manufacturing method, there is a method in which an amorphous semiconductor is deposited on an insulating substrate and then heat-treated for a long time at a low temperature (around 600 ° C.) to crystallize it (solid phase growth method).

In this case, when there is no nucleus during crystal growth, there is a problem that nuclei are randomly generated in the amorphous film, resulting in a polycrystalline film. On the other hand, there is a method in which an insulating substrate is composed of a single crystal substrate and an insulating film, and crystal growth is performed using an underlying single crystal surface as a seed through an opening provided in the insulating film. In this case, a single crystal film that inherits the crystallinity of the underlying substrate can be formed. However, since the growth distance from the single crystal seed is limited, the base opening must be periodically provided, and the effective SOI region is limited. Further, there is a problem that the substrate material is limited due to the necessity of using the underlayer seed.

There is also a method (see Japanese Patent Laid-Open No. 63-292617) in which only a crystal having a predetermined orientation is left on an insulating substrate and this crystal is used as a seed. According to this method, the substrate material of the insulating substrate is not restricted, and the degree of freedom of the SOI region to be formed can be increased. However, there is a problem that it is impossible to control the position of the seed, and it is impossible to control the rotation of the crystal axis in the plane even if the individual seeds have the same axial direction.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above various problems, and it is possible to form a single crystal semiconductor film on an insulating substrate without being restricted by the substrate material of the insulating substrate. It is an object of the present invention to provide a method for manufacturing a semiconductor thin film, which is capable of improving the degree of freedom of layout of an SOI device, improving the degree of integration, and controlling the crystal orientation of a single crystal film.

[0006]

SUMMARY OF THE INVENTION An insulating substrate having an amorphous semiconductor film formed on its surface in advance and a single crystal semiconductor substrate processed so that the surface has a plurality of protrusions are prepared separately from the insulating substrate.
Then, the two substrates are arranged and brought into contact with each other so that the surface of the amorphous semiconductor film and the surface having the protrusion shape face each other, and then the substrates are heat treated.

At this time, in the amorphous semiconductor region which is in contact with the protrusion, the protrusion is used as a seed to successively grow crystals while inheriting the crystallinity. By controlling the positional relationship between the plurality of protrusions, the solid-phase grown crystals are bound to each other before random nucleation occurs. here,
Since the protrusions are single crystals, their crystal orientations are uniform, and no grain boundaries are formed at the bonding surfaces of solid-phase grown crystals.

Next, the two substrates in contact with each other are thermally oxidized until their contact points are separated by an oxide film. Then, the substrate bonded via the oxide film is immersed in an etchant to remove the oxide film by etching, and the insulating substrate having the single crystallized thin film formed thereon and the single crystal semiconductor substrate used as the seed are obtained. To separate.

As described above, since the seed whose position is controlled and whose crystal axes are perfectly aligned is supplied from the surface side of the amorphous semiconductor film, solid phase growth is performed from this seed to form an insulating substrate. A single crystal film having a predetermined orientation can be formed on the entire surface. Moreover, since the seed is not supplied from the base, the material of the insulating substrate is not particularly selected.

Therefore, according to the manufacturing method of the present invention, the single crystal semiconductor film can be formed on the insulating substrate without being restricted by the substrate material of the insulating substrate, and the degree of freedom of the layout of the SOI element can be increased. To improve the degree of integration,
The excellent effect that the crystal orientation of the single crystal film can also be controlled is exhibited.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are views provided for explaining a manufacturing process of a silicon (Si) single crystal SOI thin film to which the first embodiment of the present invention is applied. The manufacturing process of this embodiment will be described below with reference to the drawings.

First, as shown in FIG. 1A, the main surface is the (100) plane and the orientation flat is <110.
> SiO on the surface of the single crystal Si wafer 4 in the axial direction
A mask material 6 such as _two films is formed, and the mask material 6 is patterned by known photolithography, <11
A square mask pattern having sides parallel and perpendicular to the 0> direction is formed. Then, the surface of the Si wafer 4 is etched with a KOH aqueous solution or the like.

As a result, as shown in FIG. 1B, a pyramid-shaped protrusion 4a composed of only the (111) plane can be formed on the wafer surface due to the difference in the etching rate of the crystal planes.

Further, separately on the entire main surface of a prepared Si wafer 1, sequentially depositing an insulating film 2 and the amorphous Si thin film 3 of SiO ₂ or the like '. And this Si wafer 1 and Si
After removing the oxide film on the surfaces of the wafer 4 and HF respectively,
As shown in FIG. 2A, the main surface side on which the amorphous Si thin film 3 ′ is formed and the main surface side on which the projection 4 a is formed are opposed to each other and brought into contact with each other by the projection 4 a, and then heat treatment is performed. , The amorphous Si thin film 3 ′ is crystallized. At this time, the amorphous Si thin film 3 ′ that is in contact with the protrusions 4a successively grows with the protrusions 4a as seeds while inheriting this crystallinity.
A single crystal Si thin film 3 is formed.

Here, if the mutual positional relationship of the pyramid-shaped projections 4a is controlled, the solid-phase grown crystals are bonded to each other before random nucleation occurs. The interval between the protrusions 4a can be set by the crystal growth distance during heat treatment (around 600 ° C.), but is preferably 5 μm or less in order to form a complete single crystal. Also,
Since the projections 4a are single crystals, their crystal orientations are aligned, and grain boundaries are not formed at the bonding surfaces of the solid-phase grown crystals. A load may be applied during the heat treatment in order to ensure contact between the amorphous Si thin film 3'and the protrusions 4a.

Next, as shown in FIG. 2B, the two wafers 1 and 4 are oxidized while being bonded to each other. As a result, the two wafers 1, 4 contacting each other through the tips of the protrusions 4a
Means that the oxide film 5 is present at the contact portion.

Next, by dipping this bonded wafer in an HF aqueous solution, the oxide film 5 formed in the above step of FIG. 2B is removed by etching, and as shown in FIG. 2C. The two wafers 1 and 4 are separated.

As described above, according to the manufacturing method of this embodiment, the seeds by the projections 4a of the single crystal Si wafer 4 having the uniform crystal axes are supplied from the surface side of the amorphous Si thin film 3 '.
Since the solid phase growth is performed from this seed, the single crystal Si having a predetermined orientation that can be formed by the single crystal Si wafer 4
The thin film 3 can be obtained.

Further, since the seed is not supplied from the underlayer as in the conventional case, the material of the insulating substrate is not particularly selected,
For example, a glass substrate may be used. In addition, it is possible to reduce the unevenness caused by the opening that was conventionally configured during seed formation,
Flattening can also be expected.

In the above-mentioned embodiment, the projection is formed in a pyramid shape and the tip is formed in a dot shape, but even if it is formed in a linear shape, it is formed during the separation oxidation if the contact area with the amorphous Si thin film 3'is small. The oxide film thickness can be made thin, and the difference between the Si thin film at the bonded portion and the non-bonded portion can be reduced.

Next, a second embodiment of the present invention will be described with reference to FIGS. First, a resist is applied to the main surface of the single crystal Si wafer 4 which supplies a seed, and a fine dot pattern is formed by electron beam exposure. After that, Si is etched by anisotropic dry etching to form the protrusion 4b as shown in FIG. After that, FIG.
As shown in FIG. 2C, the two wafers 1 and 4 are bonded together in the same manner as the steps shown in FIGS.
An insulating substrate having the single crystal SOI thin film 3 formed thereon can be obtained by performing heat treatment, separation and oxidation, and wafer separation using an HF aqueous solution.

When the protrusions are formed by using anisotropic etching with an alkaline solution as in the first embodiment, the height of the pyramidal protrusions may vary if the mask pattern size varies. .. In that case, when the amorphous Si thin film is contacted, there may be a part that does not partially contact. However, in this embodiment, since the protrusions 4b can be formed while maintaining the main surface of the wafer, the heights of the plurality of protrusions can be made uniform.
Here, in this embodiment, since the contact region is a surface, it is necessary to reduce this area as much as possible. However, if electron beam drawing is used, a pattern with a line width of several hundreds of A can be processed, and a separation in a post process is performed. In the oxidation, the oxide film 5 allows the two substrates to be well separated, and no problem occurs. It should be noted that the FIB device is used instead of the electron beam to directly perform S
The i-wafer 4 may be processed. Also, the protrusion 4
The height of b is preferably about several thousand Å or more so as not to hinder the supply of oxygen in the oxidation step.

FIGS. 5 and 6 are views for explaining a method for processing the seed single crystal Si wafer 4 according to the third embodiment of the present invention. In this embodiment, the protrusions of single crystal Si are formed by anodizing treatment. As shown in FIG. 5, a single crystal Si substrate 4 is prepared, an aluminum electrode plate 7 is arranged on the back surface side of the single crystal Si substrate 4, and the aluminum electrode plate 7 is exposed so that the surface of the single crystal Si substrate 4 is exposed. Cover with protective wax 8.
Then, the single crystal Si substrate 4 is dipped in an HF aqueous solution 12 having a concentration of about 25%, and the platinum electrodes 9 are arranged facing each other. And
Using the single crystal Si substrate 4 as an anode and the platinum electrode 9 as a cathode, a current is passed from a constant current source 10 to anodize the surface of the single crystal Si substrate 4.

This is because O ²⁻ and OH ⁻ are attracted to the single crystal Si substrate 4 in the HF aqueous solution 12,
On the surface of the substrate 4, electrons of O ²⁻ and OH ⁻ are deprived and active oxygen is generated. Then, due to this active oxygen, Si
O ₂ is formed on the surface of the single crystal Si substrate 4, and the SiO 2
₂ is dissolved in the HF aqueous solution 12. Anodization proceeds under such a mechanism, and a porous Si layer 4c is formed on the surface of the single crystal Si substrate 4 as shown in FIG. The porous Si layer 4c is made of quantum wires having a diameter of about several nm. In FIG. 5, 11 is an ammeter.

According to the third embodiment, the fine projections can be formed easily and inexpensively without using an expensive EB exposure device or FIB device.

[Brief description of drawings]

1A and 1B are views provided to explain a method for manufacturing a single crystal Si substrate 4 used in a first embodiment of the present invention.

2A to 2C are cross-sectional views in the manufacturing process order of the first embodiment of the present invention.

FIG. 3 is a single crystal Si substrate 4 used in the second embodiment of the present invention.
FIG. 7 is a diagram which is provided for explaining the manufacturing method of FIG.

4A to 4C are cross-sectional views in the manufacturing process order of the second embodiment of the present invention.

FIG. 5 is a single crystal Si substrate 4 used in the third embodiment of the present invention.
FIG. 7 is a diagram which is provided for explaining the manufacturing method of FIG.

FIG. 6 is a single crystal Si substrate 4 used in the third embodiment of the present invention.
FIG. 7 is a diagram which is provided for explaining the manufacturing method of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Si substrate 2 Insulating film 3'Amorphous Si thin film 3 Single crystal Si thin film 4 Single crystal Si substrate 4a, 4b, 4c Protrusion 5 Oxide film

Claims (1)

[Claims] 1. A step of preparing an insulating substrate and a single crystal semiconductor substrate having a plurality of protrusions formed on the surface thereof, and forming an amorphous semiconductor film on the insulating substrate; and the amorphous semiconductor film. A step of disposing the single crystal semiconductor substrate facing the surface on the side of the surface on which the protrusion is formed and bringing them into contact with each other; and heat treating the amorphous semiconductor film and the single crystal semiconductor substrate to form a single crystal semiconductor substrate. Crystallizing the amorphous semiconductor film by using the protrusion tips as seeds, and oxidizing until the region where the crystallized semiconductor film and the single crystal semiconductor substrate are in contact with each other is completely separated by oxide. And a step of separating the insulating substrate on which the crystallized semiconductor film is formed and the single crystal semiconductor substrate by etching away.